A 23 carat alloy with a colourful sparkle

Abstract

Lightly etched surfaces of specimens comprised of the Au-Al β'-phase exhibit a remarkable sparkling appearance and play of colour. An investigation of this phenomenon is described and explained here. The play of colour produced from individual grains as the sample is tilted in light is due to diffraction from arrays of very regular lamellae. However, consistently obtaining the desired microstructure requires an understanding of this alloy system's remarkable behaviour. Other technological properties which would be relevant to possible commercial application of this alloy are also discussed.